code: def ensure_series(X):
      assert X is not None
      if isinstance(X, list):
          return pd.Series(X)
      elif isinstance(X, np.ndarray):
          if len(X.shape) == 1:
              return pd.Series(X)
          if X.shape[1] == 1:
              return pd.Series(X.squeeze())
      elif isinstance(X, pd.Series):
          return X
      elif isinstance(X, pd.DataFrame):
          return pd.Series(X)
      raise ValueError("Failed to convert to Series")
  
file_path: fairlearn/test/unit/input_convertors.py
imports: import numpy
  import pandas
  from fairlearn.utils._input_validation import _merge_columns
label_desc: Use image node_id 5 for calling a global function with example usage: ensure_series(X) and returns: pd, pd, pd, X, pd